Start implementing regenerator

.gitignore

@@ -5,3 +5,4 @@ phpunit.xml
 vendor
 .php_cs.cache
 coverage
+a.php

src/Target/Php70/ReGenerator/ReGenerator.php

@@ -0,0 +1,212 @@
+<?php
+
+namespace Phabel\Target\Php70\ReGenerator;
+
+/**
+ * Regenerator class.
+ */
+class ReGenerator implements \Iterator
+{
+    /**
+     * Variable list for context suspension.
+     *
+     * @var array
+     */
+    private $variables = [];
+    /**
+     * Return value.
+     *
+     * @var mixed
+     */
+    private $returnValue;
+    /**
+     * Yield key.
+     *
+     * @var mixed
+     */
+    private $yieldKey;
+    /**
+     * Yield value.
+     *
+     * @var mixed
+     */
+    private $yieldValue;
+
+    /**
+     * Value sent from the outside.
+     *
+     * @var mixed
+     */
+    private $sentValue;
+    /**
+     * Exception sent from the outside.
+     */
+    private ?\Throwable $sentException = null;
+
+    /**
+     * Current state of state machine.
+     */
+    private int $state = 0;
+
+    /**
+     * Whether the generator has returned.
+     */
+    private bool $returned = false;
+    /**
+     * Whether the generator was started.
+     */
+    private bool $started = false;
+
+    /**
+     * Actual generator function.
+     */
+    private \Closure $generator;
+
+    /**
+     * Yielded from (re)generator.
+     *
+     * @var \Generator|self
+     */
+    private $yieldedFrom;
+
+    /**
+     * Construct regenerator.
+     *
+     * @param \Closure $function
+     */
+    public function __construct(\Closure $function)
+    {
+        $this->generator = $function;
+    }
+
+    /**
+     * Get return value.
+     *
+     * @return void
+     */
+    public function getReturn()
+    {
+        return $this->returnValue;
+    }
+
+    /**
+     * Start generator.
+     *
+     * @return void
+     */
+    private function start(): void
+    {
+        if (!$this->started) {
+            ($this->generator)($this->state, $this->variables, $this->yieldKey, $this->yieldValue, $this->sentValue, $this->sentException, $this->returnValue, $this->returned);
+            $this->started = true;
+        }
+    }
+
+    public function send($value)
+    {
+        $this->start();
+        if ($this->yieldedFrom) {
+            try {
+                $result = $this->yieldedFrom->send($value);
+            } catch (\Throwable $exception) {
+                $e = $exception;
+            }
+            if (!$this->yieldedFrom->valid()) { // Returned from yield from
+                $returnValue = $this->yieldedFrom->getReturn();
+                $this->yieldedFrom = null;
+                if ($e) {
+                    return $this->throw($e);
+                }
+                return $this->send($returnValue);
+            }
+            return $result;
+        }
+        $value = $this->yieldValue;
+        if (!$this->returned) {
+            $this->sentValue = $value;
+            try {
+                ($this->generator)($this->state, $this->variables, $this->yieldKey, $this->yieldValue, $this->sentValue, $this->sentException, $this->returnValue, $this->returned);
+            } catch (\Throwable $e) {
+                $this->returned = true;
+                throw $e;
+            } finally {
+                $this->sentValue = null;
+            }
+        }
+        return $value;
+    }
+    public function throw(\Throwable $throwable)
+    {
+        $this->start();
+        if ($this->yieldedFrom) {
+            try {
+                $result = $this->yieldedFrom->throw($throwable);
+            } catch (\Throwable $exception) {
+                $e = $exception;
+            }
+            if (!$this->yieldedFrom->valid()) { // Returned from yield from
+                $returnValue = $this->yieldedFrom->getReturn();
+                $this->yieldedFrom = null;
+                if ($e) {
+                    return $this->throw($e);
+                }
+                return $this->send($returnValue);
+            }
+            return $result;
+        }
+        $value = $this->yieldValue;
+        if (!$this->returned) {
+            $this->sentException = $value;
+            try {
+                ($this->generator)($this->variables, $this->yieldKey, $this->yieldValue, $this->sentValue, $this->sentException, $this->returnValue, $this->returned);
+            } catch (\Throwable $e) {
+                $this->returned = true;
+                throw $e;
+            } finally {
+                $this->sentException = null;
+            }
+        }
+        return $value;
+    }
+
+    public function current()
+    {
+        $this->start();
+        if ($this->yieldedFrom) {
+            return $this->yieldedFrom->current();
+        }
+        return $this->yieldValue;
+    }
+    public function key()
+    {
+        $this->start();
+        if ($this->yieldedFrom) {
+            return $this->yieldedFrom->key();
+        }
+        return $this->yieldKey;
+    }
+    public function next(): void
+    {
+        $this->send(null);
+    }
+    public function rewind(): void
+    {
+        if ($this->started && !$this->returned) {
+            throw new \Exception('Cannot rewind a generator that was already run');
+        }
+        $this->started = false;
+        $this->returned = false;
+        $this->returnValue = null;
+        $this->yieldKey = null;
+        $this->yieldValue = null;
+        $this->sentValue = null;
+        $this->sentException = null;
+        $this->yieldedFrom = null;
+        $this->variables = [];
+        $this->start();
+    }
+    public function valid(): bool
+    {
+        return !$this->returned;
+    }
+}